Structural angle bar



June 17 1924.

. w. J. OSULLIVAN STRUCTURAL ANGLE BAR Filed Dec. '7, 1922 PRIOR ART PRIOR ART mvenfon Patented June 17, 1924,

sir;

Jamar;

WILLIAM J. OSULIJIVAN, F NORFOLK, VIRGINIA STRUCTURAL ANGLE BAR.

Application filed December 7, 1922. Serial No. 605,496.

To all whom it may concern:

Be it known that I, WILLIAM J. OSUnLI- VAN, a citizen of the United States, residing at 529 Thirty-seventh Street, Norfolk, in

the county of Norfolk, State of Virginla,

have invented certain new and useful Improvements in Structural Angle Bars, of which the following is a specification, reference being had to the accompanying drawe object of this invention is to provide structural angle bar which while having no greater over all dimensions nor greater cross sectional area than a similarly 1 shaped structural angle bar as now made,

will at the same time resist greater stresses.

This is accomplished by providing an angle bar whose center of gravity about an axis at right angles to one of its legs, the legs being at right an les to each other, is at a greater distance rom the back of its other leg than in angle bars as now made.

In the accompanying drawings Figure 1 is a cross-sectional view of a standard angle bar as now made in which'A designates the angle bar, B its primary leg, C its secondary leg, aa an axis at right angles to its primary leg and passing throu h the center of gravit of the angle bar an m the distance of sai axis aa from the back of the secondary leg C. The nominal dimension of the angle bar A are six (6) inches extreme width of primary leg, four (4;) inches extreme width of secondary leg, and five- 'eighths (5 of one inch thickness of eachleg B and C but its actual dimensions substantially are six and one-fourth (6%) inches extreme width of primary leg, four and onefourth (4%) inches extreme width of secondso a leg and five-eighths ('3') of one Inch thlckness of each leg B and C.

Figure-2 is a cross-sectional view of an angle bar asl propose to make it, in which D designates the angle bar, E its primary e5 leg, F its secondary leg, bb an axis at right angles to its primary leg and passing throu h the center of gravity of the angle bar and y the distance of said cen er of gravity b?) from the back of its secondary to leg F. The over all dimensions and cross sectional area of the angle bar D are the same as those of the angle bar A but the thickness of its primary leg E is seventy-five hundredths (.75) of an inch and the thickness of its secondary leg F is four hundred am;l twenty-four thousandths (.424) of an we Figure 3 is a cross sectional view of a built-up structural section G com osed of four angle bars A as shown in igure 1 and a web plate H, all riveted together. The Web plate H is one-half inch by twelve (12) inches wide.

Figure 4 is a cross sectional view of a built-up structural section I, composed of four angle barsD', as shown in Figure 2 and a Web plate H, all riveted together. The over-all. dimensions and cross-sectional area of the built-up section I is the same as those of the built-up section G. The web plate is one-half (a) inch thick by twelve (12) inches wide, the same as used in the built-up section G.

All like letters in the various figures refor to identical parts.

To increase the strength of an an le bar about an axis (0-0, without increasm its over all dimensions or its cross-sectional area, I effect in the rolling of the angle bar a redistribution of the metal composing an angle bar A as now rolled by decreasing uniformly the thickness of its secondary leg C and with the metal thus saved increasing uniformly the thickness of its rimary leg B thus making what I call a thlckand-thin angle bar D, the primary leg E being the thick leg and the secondary leg F being the thin leg. The center of gravit distance x on the leg B of the angle bar becomes increased to distance 3 on the leg E of the angle bar D which increase, up to a certain point, allows a greater stress to be safely imposed upon the angle bar acting in a direction in relation to 1ts axis To better explain this I will call attention to the derivation from the moment of inertia of the section modulus and the radius of gyration, both of which are used in determining the amount of stress that is to be not allowed upon a structural part; the section modulus for parts subject to bending, as a beam, and the radius of gyration for parts subject to compression as a column or a strut, the least section modulus, which is the determining one, being the quotient of the moment of inertia divided by the distance from the center of gravity to the most distant edge or most remote fibre, and the radius of gyration being expressed as the square root of the number obtained by dividing the moment of inertia by the cross sectlonal area.

lip Figure 1 the standard angle bar A. has a cross sectional area of six and fourteen hundredths (6.14) square inches, a distance it of two and six hundredths (2.06) inches, a moment of inertia of twenty-three and twenty-nine hundredths (23.29) a least section modulus of five and fifty-six hundredths (5.56), and a radius of gyration of one and ninety-five hundredths (1.95), as calculated in inches about axis a-a.

In Figure 2 the thick-and-thin angle bar D as I propose to make it has a cross-sectional area of six and fourteen hundredths (6.14) square inches the same as angle bar A, a distance 1 of two and thirty-nine hundredths (2.39) inches, a moment of inertia of twenty-five and two hundredths (25.02) a least section modulus of six and ninety-three hundredths (6.93) and a radius of gyration of two and two hundredths (2.02), as calculated in inches about axis As the beam strength of a structural .part increases directly as its least section modulus is increased, it is apparent from a comparison of the section moduli of the two angle bars A and D that although the over all dimensions and the cross sectional area of the angle bar D are the same as those of the angle bar A the beam strength of the angle bar D about its axis 6-?) is twentyfour (24%) per cent greater than the beam strength of the angle bar A about its corresponding axis aa.

Also, as the column or strut strength of a structural part increases when its radius of gyration is increased, it is apparent from a comparison of the radii of gyration of the two angle bars A and D that, although the over all dimensions and the cross sectional area of the angle bar D are the same as those of the angle bar A, the column or strut strength of the angle bar D about its axis b-Z is greater than the column or strut strength of the angle bar A about its corresponding axis -0:a. Applying the well known column formula of p:160007O 1/?" in which 1 is the column length in inches, 1* the radius of gyration as calculated in inches and p the allowed compressive stress per square inch of cross sectional area, it will be found that for a length of twenty feet (20'0") the angle bar A will safely sustain the equivalent of a compressive load of forty-five thousand three hundred (45,300) pounds in relation to its axis a-a, while the angle bar D will safely sustain the equivalent of a compressive load of forty-seven thousand two hundred (47,200) pounds in relation to its corresponding axis eshes 5-5, or four and two-tenths percent (4.2%) more than will the angle bar A.

In Figure 3 the built-up section G composed of the four angle bars A and the web plate H has a cross sectional area of thirtyand fifty-six (30.56) hundredths square inches, distances w of two and thirty-one hundredths (2.31) inches, a moment of inertia, of two hundred and fourteen and twenty-eight hundredths (214.28), a section modulus of thirty-two and ninety-five hun dredths (32.95) and a radius of gyration of two and sixty-five hundredths (2.65) as calculated in inches about axis a'a'.

In Figure 4 the built up section l composed of four angle bars D has a cross sectional area of thirty and lift -six hundredths (30.56) square inches, t e same as the built-up section E, distances y of two and sixty-four hundredths (2.64) inches, a moment of inertia, of two hundred and seventy-five and forty hundredths (275.40) inches, a section modulus of forty-two and thirty-seven hundredths (42.37) as a radius of gyration of three (3.00) as calculated in inches about axis b-5.

It is apparent from a comparison of the section moduli of the two built up sections G and l that, although the overall dimensions and the cross-sectional area of the section l are the same as those of the section Gr the beam strength of the section ll about its axis b--b is twenty-eight and fivetenths percent (28.5%) greater than the beam strength of the section E about its corresponding axis a-a..

Also, it is apparent from a comparison of the radii of gyration of the two sections G and l that, although the overall dimensions and the cross sectional area of the section l are the same as those of the section G, the column or strut strength of the section I about its axis 72' -15 is greater than the column or strut strength of the section G about its corresponding axis if-a. Applying the herein previously used column formula it will be found that for a length of thirtyfeet (30'0") the section G will safely sustain a compressive load of two hundred and eight thousand (208,000) pounds in relation to its axis a"-a' while the section l will safely sustain a compressive load of two hundred and forty-two thousand (242,000) pounds in relation to its corresponding axis b-l'), or eleven percent (11%) more than will the section G.

This invention consists essentially in producing a structural angle bar whose center of gravity on an axis at right angles to one of its legs is more distant from the baclr of its other leg, this distance hereinbefore being called distance 00 and distance 3 than on any angle bar now made, each of whose legs is of uniform thickness, and whose over all dimensions and cross-sectional area are ghe same as on this newly invented angle ar. No structural angle bar having legs of uniform thickness that I am aware of is made whose center of gravity distance it as hereinbefore described is greater than thirty-eight percent (38%) of the extreme width of the leg for which this center of gravity distance a: is calculated, and no structural angle bar, having legs of uniform thickness that I am aware of is made, the extreme width of one of whose legs being not less than sixty-seven percent (67%) of the extreme width of its other leg, whose center of gravity distance :1; on said other leg is greater than thirty-fonr and five-tenths percent (34.5%) of the extreme width of the leg for which this center of gravity distance m is calculated.

What I claim is:

1. A structural angle bar neither of whose legs is less than two (2") inches in extreme width, having each leg substantially of uniform thickness except for edge roundings and angle fillets, one leg being thicker than the other leg.

2. A structural angle bar whose legs being each of substantially uniform thickness except for edge roundings and angle fillets, the center of gravity of which angle bar on an axis at right angles to one of its legs is situate not less than thirty-eight (38%) percent of the extreme width of said leg from the back of its other leg.

3. A structural angle bar whose legs being each of substantially uniform thickness except for edge roundings and angle fillets, the extreme width of one leg being not less than sixty-seven percent (67%) of the extreme width of the other leg the center of gravity of which angle bar on an axis at right angles to one of its legs is situate not less than thirty-four and five-tenths percent (34.5%) of the extreme width of said leg from the back of its other leg.

WILLIAM J. OSULLIVAN. 

